About 15 years ago, long before he was primarily known as a wonkish proponent of utility cycling, or the idea that bikes should be ridden to get somewhere rather than for sport, Joe Breeze was downing beers at a party in Northern California. He was surrounded by trendsetters such as Keith Bontrager (who made the first great mountain bike wheels) and Gary Fisher (who has since laid claim to the unofficial title of father of the sport)-visionaries who, like him, were at the hip, red-hot center of the red-hot sport of mountain biking.

Breeze belonged at the bash because he had built the world's first real mountain bike, and was famous for his elegant, sweet-handling machines. In 2002, he would abandon his off-road roots and begin producing a noble line of bicycles designed only for city riding and commuting, but at the time he was an icon of the wildest sport going. So, without the benefit of hindsight, it was surprising to hear Breeze give a nuanced, far-reaching and accurate answer when someone asked, just making party conversation, "Can bikes really save the world?"

"Wrong question," Breeze said. With a hand holding a red plastic beer cup he gestured around the room at the cycling cognoscenti. "The real question is how can we get enough people on bikes to save the world?"

The Answer
We had many hopes when we began our BikeTown project by giving free bikes to 50 residents of Portland, Maine, in 2003. But solving Breeze's puzzle wasn't one of them. The Treks we gave away went to 1/46th of 1 percent of Portland's population, an inconsequential ratio that shrank even more as we expanded the program, raising the total number of free bikes to 250 in 2004 but spreading them across five cities.

The math was clear: Every bike we gave away possessed the power to spark an individual triumph, but all of them together seemed unlikely to ignite a social revolution.

The stories that came from each of our BikeTowns reinforced the lesson. In Portland, the first 50 BikeTowners burned 751,841 calories in just three months. People shed pounds, stopped smoking and strengthened themselves after illnesses, in one case going from kidney transplant patient to competitive bike racer. Seventy-two percent said that cycling improved their family and social relationships. The personal testimonials racked up in 2004: 92 percent of the 250 BikeTowners said cycling had a positive impact on their lives, 70 percent of those who rode at least 10 miles per week reported higher self-esteem, and nearly half said they became closer to their children thanks to the bike.

Change lives? You bet. Change the world? When we expanded BikeTown once again, to 20 cities and 1,000 bikes in 2005, the total of all the giveaways over three years-1,300-was still too small a fraction of the U.S. population (never mind the world) for us to give the idea serious consideration.

But it was in that '05 group's long list of what by now had become almost routinely amazing statistics that we discovered a possible answer to Joe Breeze's vital question-embodied by BikeTowners like Kristi Kayler, a 31-year-old educational consultant and recreational runner from North Phoenix, Arizona.

She got her Schwinn in June because she wanted to boost her fitness by riding the 10 miles to work three or four days a week. When she began spinning around the city on summer weekends for fun, she says, her boyfriend, Kurt, pedaled along. Impressed by Kristi's commitment-she commuted even in 115-degree heat-her 59-year-old father, Keith, started riding an old hybrid to do short errands. Her sister Kimberly, a marathoner, tagged along on a few weekend rides on a borrowed bike, fell in love with the sport and got a new road bike for Christmas. Kimberly's five-year-old son, Joel, began asking to enter the kiddie races sometimes held before adult competitions.

"Before one race," Kristi says, "Joel turns to his mother and says, 'We need to talk to Aunt Kristi to discuss strategy.' I don't think he realizes all I was doing was commuting." Johan Bruyneel she is not. But, like his new favorite athlete, Lance Armstrong, Joel won the race-and got his picture in the local paper.

Each BikeTowner directly inspires an average of 3.6 other people to start or resume cycling, a ripple of enthusiasm that just might be strong enough to wash across the entire world.

Bike Fever
In the U.S., bicycles have proved stubbornly, and unfortunately, resistant to what Malcolm Gladwell, in his book The Tipping Point calls social epidemics-the rapid spread of an idea or product that sweeps across society like a cold virus.

One of the most compelling examples Gladwell cites is that of Hush Puppies. In late 1994, he writes, the venerable American brand was nearly dead. It sold only 30,000 pairs and was scheduled to be phased out by its parent company. Then, reports Gladwell, a stylist at a fashion shoot in New York City told executives that "a handful" of club-scene hipsters were scouring resale shops for Hush Puppies, which had become so uncool they were cool. The designer Isaac Mizrahi began wearing them. The next year, Hush Puppies sales leaped to 420,000 pairs. In 1996, Hush Puppies quadrupled sales to more than 1.6 million pairs, won a prize for best fashion accessory, and was on the way to becoming a staple of every mall in America-all in just two years.

In contrast, bikes are stable. Sales rise and fall from year to year, and segments of the sport gain popularity-mountain bikes in the '90s, road bikes at the start of the millenium, occasional spurts from niches such as recumbents or singlespeeds-but there's no feverish growth.

Retailers estimate that they sold about 20 million bikes in the U.S. in 2004, according to the Bikes Belong Coalition, about the same amount sold in 2000, before sales dipped to 16.6 million in 2001 and began slowly climbing again, according to Bicycle Retailer and Industry News. The top figure from the 1970s: about 20 million. Despite spikes in popularity driven by Greg LeMond in the '80s, by the popularity of extreme sports like mountain biking in the '90s, and by Lance Armstrong in the late '90s and early this decade, new cyclists enter the sport in long-term, bell-curve market fluctuations, not through a revolutionary social epidemic.

The question is: Can BikeTown change that? Take a ride with Keith Look, and you'll probably say yes.

Look is the 33-year-old principal of Meyzeek Middle School in Louisville, Kentucky. The school he runs is named for Albert E. Meyzeek, a civil rights activist in a city with a long history of racial segregation; it sits in one of the city's poorest districts, Smoketown, but because of magnet programs in math and science it also draws students from the richest parts of the city.

We gave Look a Schwinn so he could pedal the flat mile-and-a-half between his home and his school, riding among the 300 sixth-, seventh- and eighth-graders out of the total of 1,100 who don't rely on a bus or car for transportation.
Of those 300-all of whom enjoyed shouting at Look as he passed, he says-he estimates that maybe 20 ride bikes to school on any given day. Look is an enthusiastic but resolutely humble person, so loathe to boast that he'll barely acknowledge that the number of bikes in the school rack occasionally went as high as 50 once he began riding. An educator at heart, he'd rather talk about what he learned.

He ticks off the list: "Riding with a tie on poses more of a challenge than you think. It's socially unacceptable to show up to a business meeting sweating." Look laughs, pauses a moment, and says with a deeper timber in his voice, "There needs to be a serious, ongoing public service campaign to teach drivers how to interact with cyclists on the road. That absolutely stands out."

Perhaps coincidentally, this year Look's hometown earmarked funds from a Robert Wood Johnson Foundation grant to develop a Safe Routes to School program, a national advocacy project that identifies, marks, improves and publicizes the best commuting paths for schoolkids.

Though Kayler's happy-go-lucky fitness commutes and Look's earnest community outreach on wheels could hardly be any more different, both are what social scientists, marketers and demographic experts call an influencer, the necessary start of the kind of rapid makeover Gladwell describes.

"The more expensive the product we're giving away, the more we target only the influencers," says Lucas Beddows, president of On-Point Marketing, a company that has organized promotions and giveaways for Taco Bell, McDonald's, Performance Bicycles and other top businesses. "You can stand on the street and give away jelly beans. But for a promotion of $100 headsets we gave them to only 1,000 carefully selected subjects, like recording industry businesspeople and doormen at hot clubs-trendsetters."

There's good evidence that just about anybody riding a bike becomes an influencer. No one has ever done a long-term, quantifiable study of how many new riders the average cyclist brings into the sport, but two subscriber studies done by bicycling provide clues. In 2002, we found that 84 percent of our readers were asked for advice about what bike, components or clothing to buy, and that the advice was followed 88 percent of the time. An earlier study yielded similar results. And in each study, the median number of advice seekers was just over 4-a number close to the 3.6 cyclists each BikeTowner directly inspired.

Medians and averages being what they are, there are BikeTowners like 25-year-old Erika Forster, who asked for a Giant so she could ride to band practice in Brooklyn, and who can name 10 friends who began riding thanks to her. Sometimes the number of direct influences is smaller, or at least harder to quantify. Even then, the program ripples in surprising ways. Shelley Bruder, 51, teaches indoor cycling in Ann Arbor, Michigan, and asked for a Schwinn so she could ride outside. Most of her class already biked outdoors, and may have gotten out more when they began meeting her occasionally for weekend rides, but she says her direct influence is hard to track, except for one student.

Bill Gabriel, a 51-year-old psychiatrist who lost 40 pounds as part of Bruder's pack, explains that when he finally felt fit and confident enough to "pull out my multispeed whatever," his 10- and 12-year-old sons asked to go along, and quickly became enthusiastic and regular cyclists. "My wife started as well," Gabriel says, "but the weather got crummy."

No expert-not The Tipping Point's Gladwell or the promotion guru Beddows or any other source we contacted-could predict the birthrate or lifespan of these ripples. Likewise, no one can estimate how many free bikes it might take to achieve what Gladwell calls the tipping point, the moment when an idea or product leaps from its small core of influencers to mass acceptance with a snap like a fire starting from a spark.

All we know for sure is this: That's one confirmed ripple from Bruder, and two or three ripples from her ripple, and the end of the cycle is nowhere in sight.

So What?
What if we never give away that magic number of bikes? And what if the ripples of enthusiasm Shelley Bruder spins out of her stationary bike go no farther than Bill Gabriel, and his sons get an Xbox 360 and never touch their bikes again?

Will BikeTown have failed as a social movement?

Or, conversely, why should you want it to succeed? How, specifically, would a biking society be better? One thing we know is that regular aerobic exercise, such as cycling, reduces chronic illnesses-so says a 300-page, landmark summary of hundreds of studies, jointly published in 1996 by the Surgeon General, the U.S. Department of Health and Human Services, the Centers for Disease Control and Prevention and the National Center for Chronic Disease Prevention and Health Promotion. We also know, according to a 1996 study in the Journal of the American Medical Association, that the health-care costs of people who suffer mainly short-duration maladies such as colds and flus is just $817 annually, as opposed to the $3,074 spent on people afflicted with the chronic illnesses associated with a sedentary lifestyle. So it's possible that your health insurance premiums could go down. Another figure: According to calculations done by bicycling, by riding to work instead of driving just one day per week, the average American (who drives 29 miles daily) would annually save $611 in gas and depreciation-a slight uptick in discretionary income that might benefit the economy, if it's not offset by the losses from, say, the guys at the auto garage who'd perform fewer repairs and sell less gas.

Would there really be fewer fights for the good parking spots, or less road rage? (Think of the sprint on your last training ride.) Would all those Nascar, pigskin and hoops fans really transfer their loyalty to a three-week race in France just because they start getting grease marks on their right calves?

The real benefits of a bike utopia can seem hazy. Here's one that's clear: BikeTown makes your own bicycle more valuable.

In his book, New Rules for the New Economy, Kevin Kelly identified a principle he calls the law of plentitude, which contradicts one of the most basic and familiar economic laws: supply and demand. Products in what Kelly calls a closed system, such as diamonds, derive value traditionally, from scarity; the lower the supply, the higher the demand and value. But products in what Kelly calls a network economy gain value as they spread. The first fax machines, he writes, were available in 1965 and cost about $1,000 each but in terms of value were practically worthless. Who could you fax? Today, a fax machine costs just about $200 but gives you access to a $3 billion network of other fax machines.

Think cell phones, pagers, Internet auction sites-and bikes.

The more people there are on bikes, the more value your own bike has. Its social value rises because you have access to a larger network of potential friends and romantic interests. Its value as a fitness machine rises as you gain training partners. Its value as a vehicle rises when the owner of a deli puts a bike rack out front.

Friends scoffed when I tried to explain that their $5,000 road racers became more valuable because bicycling was giving away $200 hybrids-until I was able to tell them about Karen Gardner, a 42-year-old who wanted a Giant to begin commuting the 5 miles from her home in Westchester, New York, to her job in media relations at the Albert Einstein College of Medicine in the Bronx.

About 90 percent of her commute is on bike paths, Gardner says. "One day I was riding to work and at an intersection I had to stop, get off my bike and lift it over a high curb. I questioned my memory-how did I not remember this curb? It took me a month to convince myself that the curb hadn't been there originally."

Gardner found out that a construction crew working on adjoining roads had put in new curbs, replacing the sloped transitions that had let cyclists previously ride the path uninterrupted. She contacted the Bronx borough president, the parks department and the department of transportation, explaining to each that change had made the path less usable and less safe. She was told no one else had complained.

But two months later, sloped curbs were reinstalled.

Gardner says sometimes now as she rides back and forth to work she thinks about the idea that if she hadn't joined BikeTown, she never would have had to stop for that curb. And that, maybe, instead of just a single voice of dissent there would have been none. "Winning this bike," she says, "it's sort of like kismet."

She begins, then, to muse about other bikes she's owned, about the little blue Schwinn she rode as a child in Brooklyn, about the banana-seat-and-sissy-bar bike she inherited from her older brother, the first 10-speed she got in junior high, a rhapsody of memories that ripples forward from nearly as far back as she can remember being alive. "One of my favorite things to do when I was young," she says, "was to go riding, and take a random turn and get lost, not knowing how far I'd go."